The present invention relates to a method for operating a wireless terminal as an access point—access point terminal—that connects a set of one or more client terminals to an external network, wherein a schedule of absence periods is established during which said connected client terminals are not allowed to transmit data to said access point terminal, wherein the absence periods together with corresponding presence periods are scheduled at regular intervals and have certain durations.
Furthermore, the present invention relates to a wireless terminal being operated as an access point—access point terminal—that connects a set of one or more client terminals to an external network, wherein said access point terminal is enabled to establish a schedule of absence periods during which said connected clients are not allowed to transmit data to said access point terminal, wherein the absence periods together with corresponding presence periods are scheduled at regular intervals and have certain durations.
In recent years it has become commonly known to operate wireless or handheld devices, like e.g. mobile phones, laptops, cameras or tablets, in such a way that they act as access point for other devices—client terminals—providing them with access to an external network. A typical application scenario would be, for instance, a mobile phone being equipped with a 3G interface and a Wi-Fi interface. In this scenario, the mobile phone may act as an access point in the Wi-Fi network and may give access to the 3G network to the attached Wi-Fi clients.
In contrast to conventional stationary base stations, which are noncritical in terms of energy supply as they are constantly plugged to the power, in the case of wireless terminals the problem arises that they are typically battery-powered and, acting as access points, quickly drains the batteries of the devices. Therefore, all such devices need to be power efficient when acting as APs. However, setting a wireless terminal that acts as access point, e.g. as Wi-Fi AP, into a sleep state in order to save power, comes along with the risk of causing degradation on the QoS experienced by the connected clients.
As a relevant prior art approach there is the P2P Technical Specification developed by the Wi-Fi Alliance, which is marketed under the name Wi-Fi Direct and which is expected to be launched in the second half of 2010 (see for reference Wi-Fi Alliance Technical Committee, P2P Technical Group, “Wi-Fi Peer-to-Peer (P2P) Technical Specification v1.0”. Section 3.3.3.2 “P2P Group Owner Notice of Absence Procedure”). The new Wi-Fi Direct technology enables easy device to device connectivity using the Soft-AP concept. In this context Soft-AP denotes a device that implements a dual STA/AP stack.
The specification defines a power saving protocol that allows a Wi-Fi AP to save power [1, section 3.3.3.2]. The power saving protocol is named “Notice of Absence (NoA)”, and it allows an AP to establish an absence schedule where the associated clients can not transmit in the network. The established absence periods can thus be used by the Wi-Fi AP to save power. However, although the P2P Technical specification defines the signaling protocol required to achieve power saving in a Wi-Fi AP, it does not define how such an absence schedule has to be built.
Another approach for reduced power consumption in a wireless access point is described in U.S. Pat. No. 7,436,790 B2. The major contribution of this work is a method to save power in a Wi-Fi AP by means of using “Contention Free Periods (CFPs)”. CFPs are another signaling mechanism defined in the 802.11 standard. However, this mechanism is far less flexible than the NoA protocol discussed above, because a CFP can only signal a single absence period between two beacons. In addition, the CFP mechanism is not widely deployed in the market.
It is therefore an object of the present invention to improve and further develop a method and a wireless terminal of the initially described type in such a way that, by employing mechanisms that are readily to implement, an efficient and flexible power saving is achieved for the wireless access point without significantly degrading the performance and QoS experienced by the connected client terminals.